Current deposition techniques for growing silica uniformly and conformally on substrates rely on binary gas phase reactions, such as the following three combinations of reactants:
trimethylaluminum (TMA) alternately deposited with tris(tert)butoxyl silanol;
ammonia (NH3) alternately deposited with tetramethoxysilane; or
H2Si[N(C2H5)2]2 alternately deposited with oxygen plasma.
However, these techniques suffer from certain limitations. First, alternating layer deposition techniques using binary gases deposit film on all exposed surfaces, requiring periodic maintenance/cleaning of the interior reaction chamber surfaces. Second, at least one of the reactants described above are either toxic (e.g., NH3), explosive (O2) or pyrophoric (TMA). Third, the byproducts, such as ammonia, methane, amides, and the like, from each of these vapor phase silica reactions must be handled with appropriate caution.